Superconductor and process of manufacture

Abstract

A method for producing a superconductor by partial inter diffusion of layers of metal under a diffusion heat treatment to provide a ductile beta phase alloy, along with undiffused metal layers to permit ease of extrusion and drawing to fine layer thickness. At some point in the reduction the layers are further diffused to give an alloy superconducting product which is optimal for the high field (5-9 T) of interest in contact with a non-superconducting layer. This optimal diffusion is preferably accomplished after a sufficient reduction such that the individual metal layers are 2.5-15 microns thick.

We claim: 
     
       1. A method for producing a superconductor, which is optimally superconducting at a high field on the order of 5-9 T, comprising the steps of combining a plurality of metal bodies to form a composite structure, said metal bodies being selected from the groups consisting of the transition metals niobium, tantalum, titanium, zirconium and vanadium, alternate bodies being formed of different transition metals to form pairs, reacting the transition metals to cause diffusion of at least one metal into the other metal to form a ductile alloy as a result of this diffusion, limiting the extent of the reaction to less than the amount necessary to produce an optimal superconducting alloy in said pair of transition metals mechanically reducing the composite structure and providing further diffusion to produce in each said pair an optimal superconducting layer in contact with a layer which is non superconducting at said high field, each said layer being less than 1000 Angstroms thick; the diffusion process being conducted in multiple steps interspersed with mechanical reduction steps, each diffusion step being limited in time and temperature to avoid unwanted grain growth and grain boundary diffusion in each transition metal zone. 
     
     
       2. A method for producing a superconductor comprising the steps of combining a plurality of metal layers to form a composite structure, said metal layers being selected from the group consisting of the transition metals niobium, tantalum, titanium, zirconium and vanadium, and alloys thereof alternate layers being formed of different transition metals to form pairs, reacting the transition metals to cause diffusion of at least one metal into the other metal to form a ductile alloy as a result of this diffusion, limiting the extent of the reaction so as to maintain some undiffused transition metal along with the ductile alloy in at least one of each said pair of transition metals mechanically reducing the composite structure and providing further diffusion to produce a superconducting layer in contact with a non superconducting layer in each said pair, each said layer being less than 1000 Angstroms thick; the improvement wherein the thickness of each initial metal layer being reduced by a factor of at least 1000 and the diffusion process being conducted in multiple steps interspersed with mechanical reduction steps, each diffusion step being limited in time and temperature to avoid unwanted grain growth and grain boundary diffusion in each transition metal zone. 
     
     
       3. A method for producing a superconductor comprising the steps of combining a plurality of niobium and titanium layers to form a composite structure, alternate layers being formed of niobium and titanium to cause diffusion of at least one transition metal into the other metal to form a ductile NbTi alloy as a result of this diffusion, mechanically reducing the composite structure and providing further diffusion to produce an optimal superconducting NbTi layer in contact with a non superconducting layer in each said pair, each said layer being less than 1000 Angstroms thick; the thickness of each initial metal layer being reduced by a factor of at least 103 and the diffusion process being conducted in multiple steps interspersed with mechanical reduction steps, each diffusion step being limited in time and temperature to avoid unwanted grain growth and grain boundary diffusion in each transition metal zone. 
     
     
       4. Method for producing a superconductor which is superconducting at a high field and low temperature comprising the steps of combining a plurality of metal layers to form a composite structure, said metal layers being selected from the group consisting of the transition metals niobium, tantalum, titanium, zirconium and vanadium, and alloys of such metals, alternate layers or groups of layers being formed into an assembly having different transition metal layers, reacting the transition metals to cause diffusion of at least one metal into the other metal to form a ductile alloy as a result of this diffusion, limiting the extent of the reaction so as to maintain zones of transition metal and transition metal alloys which are not superconducting at said high field along with the ductile alloy, mechanically reducing the composite structure and providing further diffusion to produce a final layer which is superconducting at said field, said superconducting layer being in contact with a final non superconducting layer in each said assembly, each said final layer being less than 1000 Angstroms thick; the diffusion process being conducted in multiple steps interspersed with mechanical reduction steps, each diffusion step being limited in time and temperature to avoid unwanted grain growth and grain boundary diffusion in each transition metal zone. 
     
     
       5. The method of claim 4 wherein said superconducting layer comprises a ternary alloy.